1. Field of the Invention
The present invention relates generally to optical readers, and more particularly to an optical reader that changes a light scanning direction. The optical reader of the present invention is especially suitable for barcode scanners which optically read a barcode put on merchandises in POS systems and the like.
2. Description of the Related Art
Recently, barcode scanners have become more frequently used for cashiers in supermarkets, discount stores, home centers, etc. In general, operators who use a barcode scanner fixed onto a cashier table move a merchandise on which a barcode is printed, whereby the merchandise may pass across a scanning pattern emitted in a predetermined direction from a read window of the barcode scanner.
The scanning pattern is usually fixed to one pattern, and its emitting direction is preset and fixed in accordance with the installation and usage environments of the scanner at the time of manufacturing. The “installation environment”, as used herein, means a direction in which the read window is to be installed in a cashier table; more concretely, whether the read window is arranged parallel or perpendicular to the cashier table. The former barcode scanner is called a lateral type, and the latter a longitudinal type. The “usage environment”, as used herein, means a moving path of a merchandise onto which a barcode is printed; for example, whether the merchandise is to be moved from right to left or left to right, even in the same lateral type. The usage environment depends upon each operator's height, experience and the like.
The emitting direction is usually preset and inclined by a predetermined angle relative to a direction perpendicular to the read window, toward an upper stage from which a merchandise comes (for instance, which is a right side if the merchandise moves from right to left).
With the spread of barcode scanners, prompt reading of barcodes and efficient manufacturing of the barcode scanners has been strongly demanded.
However, the conventional longitudinal and lateral barcode scanners are different in manipulation and optimal scanning-pattern emitting directions. Even in the same lateral type, a proper emitting direction is different between one which moves merchandise from right to left, and another which moves merchandise from left to right. Therefore, in an attempt to install and use the conventional barcode scanners each store has ordered apparatuses having a different pattern emitting directions which correspond to their installation and usage environments.
A change of the emitting direction requires a change of inclination of an optical system that generates a scanning pattern and/or an arrangement of optical element(s). Consequently, each barcode scanner, even for the same type, should be manufactured differently in emitting direction for every business type of different installation and usage environments, causing inefficient manufacturing and price increasing. On the other hand, primarily for manufacturing purposes, there have been proposed apparatuses having a fixed emitting direction while the installation and usage environments are ignored, but these apparatuses cannot generate an optimal pattern to achieve an object of prompt reading.
On the other hand, the actual prompt reading depends, in addition to the scanning pattern, upon a moving path of merchandise (or barcode) by an operator. Even in a barcode scanner in which the scanning pattern is fixed to the optimal pattern for the installation and usage environments, a moving path slightly different among operators depending upon their heights, experiences, skillful hands, habits, etc. Disadvantageous, each operator must adjust a barcode moving path and spend along time to master the operating skill.
To eliminate these problems, applicant has proposed, in Japanese Laid-Open Patent Application No. 9-16705, a barcode reader that generates a plurality of scanning patterns by making mirrors movable in the optical system, extending a scan area, and selecting one frequently used scanning pattern from them. Nevertheless, this invention was disadvantageous because it has a low reading reliance and does not always meet operative safety requirements.
The scanning pattern frequently used in this reference is not the actual optimal scanning as a result of simulation taking into account the arrangement between a laser source and a light receiving element, while minimizing optical noises caused by mirror angles and the light amount of the laser beam. A scanning pattern including optical noises, even though hitting a barcode, cannot properly read the barcode data. For instance, a certain mirror angle puts the reflected light over the store's light as a noise, and the light receiving element receives a large amount of incident light. A laser beam reflected at an edge or the like of the reflection mirror also causes a large amount of light incident to the light receiving element. In this way, a plurality of scanning patterns which have been generated only by taking into account the usage environment without paying attention to the optical noises would lower the reading reliance and delay the reading time. It is preferable to maintain the optimal scanning pattern that is set at the time of manufacturing.
In addition, as seen in the International Standard IEC and the U.S. Standard CDRH, which take care of human eyes subject to a laser beam, the laser safety standards define certain restrictions regarding the light amount of an incident laser beam. However, the light amount of an arbitrarily changed scanning pattern would not necessarily meet the above standards, thereby endangering safety.